1. Field of the Invention
The present invention relates to a light source module, and particularly to a light source module having a better color rendering index (CRI) and a higher color stability.
2. Description of Related Art
FIG. 1 is a schematic view of a conventional light source module. Referring to FIG. 1, a conventional light source module 100 is adapted to be applied in a projection device to provide an illumination beam required for the projection device. The light source module 100 includes a red light emitting diode (red LED) 110r, a green light emitting diode (green LED) 110g, a blue light emitting diode (blue LED) 110b, a reflection mirror 120, two dichroic mirrors 130a and 130b, and a light integration rod 140. Further, the red LED 110r, the green LED 110g and the blue LED 110b provide a red light 112r, a green light 112g and a blue light 112b respectively.
The reflection mirror 120 reflects the red light 112r to the dichroic mirror 130b, and the dichroic mirror 130b is capable of allowing the red light 112r to pass through and reach the light integration rod 140. The dichroic mirror 130a allows the green light 112g to pass through and reach the dichroic mirror 130b, and the dichroic mirror 130a reflects the blue light 112b to the dichroic mirror 130b. The dichroic mirror 130b reflects the green light 112g and the blue light 112b to the light integration rod 140. The light integration rod 140 homogenizes the red light 112r, the green light 112g and the blue light 112b. 
FIG. 2 is a normalization spectrum of a red light, a blue light and a green light provided by a conventional light source module. Referring to FIG. 2, it can be observed from FIG. 2 that wavelengths of the red light 112r, the green light 112g and the blue light 112b provided by the conventional light source module 100 are discontinuous within a wavelength range of visual lights. Accordingly, when the red light 112r, the green light 112g and the blue light 112b are mixed into a white light, a color rendering index (CRI) of the white light is low (only within 50-75).
Moreover, since a light-emitting wavelength of a light emitting diode (LED) tends to drift as a temperature of or an electrical current introduced into the LED varies, the color coordinate points of a monochromatic light on a CIE1931 chromaticity diagram are inaccurate, and colors obtained from mixing the red light, the green light and the blue light are unstable. As a result, imaging quality of the projection device is affected.